In a 3GPP LTE-Advanced system (LTE stands for Long Term Evolution which is an evolved system of a third-generation mobile communication system, and an LTE-Advanced system is an upgraded LTE system), new technologies such as high-order MIMO, Coordinated Multi-Point transmission technology will be adopted to improve the performance of the system.
In view of these new technical features, the LTE-A system adopts a dedicated pilot to demodulate data, and pilots are kept orthogonal between respective streams. For a transmission scheme with the number of streams being 1 and 2, pilots of two streams are orthogonal in a CDM mode; for a transmission scheme with the number of streams being 3 and 4, pilots of four streams are in a hybrid FDM and CDM mode; and for a transmission scheme with the number of streams being 5, 6, 7 and 8, pilots of eight streams are in the hybrid FDM and CDM mode. As can be seen, the CDM orthogonal mode is involved for pilots in all the transmission schemes. However a Walsh code or a normalized Walsh code is adopted as a pilot in the CDM mode, thus resulting in different power over two adjacent OFDM symbols where the pilot is located.